LU-14159 build: fix gcc8 warnings on kthread_run calls

LU-14159 build: fix gcc8 warnings on kthread_run calls

Fixes warnings from gcc8 about kthread_run calls with no format
parameter.

Signed-off-by: Quentin Bouget <quentin.bouget@cea.fr>
Signed-off-by: Sebastien Piechurski <sebastien.piechurski@atos.net>
Change-Id: I30a68a1d0e318c98f2da547ece8018564ced69c0
Reviewed-on: https://review.whamcloud.com/40790
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: Maloo <maloo@whamcloud.com>